The present invention relates to a disk control device and, more particularly, to a disk control device for controlling the positioning of an optical disk having address sections in each of which a plurality of identical track addresses and a plurality of identical sector addresses are written.
A disk control device of the type described is customarily constructed to control the positioning of an optical disk on the basis of the result of comparison of track addresses and sector addresses which are preformated on the disk and written in address sections of the individual sectors with a particular address for starting writing data, as disclosed in U.S. Pat. No. 4,638,472. Specifically, data are written when m of each of N sector addresses and N track addresses (N&gt;m) which are preformated on an optical disk are coincident with a designated address. If none of the addresses is coincident with the designated address, data are written in an alternative sector by leaving that sector empty.
A problem with the above-described prior art disk control device is that even if data are successfully written in any sector under the coincidence of all the track and sector addresses, a scratch produced in the address section associated with that sector after data writing would prevent the disk from being positioned in the event of reading out the data. Another problem arises from the fact that data cannot be written in a sector unless the track and sector addresses assigned to that sector are coincident with an address for starting writing. Specifically, assuming that data were written in an address or sector other than the address or sector coincident with the address for starting writing, i.e., alternative address or sector, whether the sector of that address is purely empty or forcibly left empty because data could not be written therein has to be determined at the time of reading by tracing back to the alternative sector. Such a decision consumes a disproportionate period of time.